Process for the preparation of acrylic acid

ABSTRACT

IN THE PREPARATION OF ACRYLIC ACID BY THE GAS PHASE CATALYTIC OXIDATION OF ACROLEIN WITH MOLECULAR OXYGEN IN THE PRESENCE OF STEAM, A PROCESS WHEREIN THE OXIDATION IS EFFECTED N THE PRESENCE OF A CATALYST COMPOSITION CORRESPONDING TO THE FORMULA: MOA BB(LI2 SO4)COD WHEREIN A, B AND D REPRESENT RESPECTIVELY THE NUMBER OF ATOMS AND C IS THE MOL NUMBER OF LITHIUM SULFATE, AND WHEREIN A IS 12, B IS 0.1 TO 9/0, C IS 0.1 TO 9.0 AND D IS 36.25 TO 58.5. THE CATALYST COMPOSITION HAS A HIGH CATALYTIC ACTIVITY WITH A LONG CATALYTIC LIFE, AND ACRYLIC ACID IS PRODUCED IN AN EXCELLENT YIELD WITH A HIGH PURITY BY THE USE OF SUCH COMPOSITION.

United States Patent US. Cl. 260-530 N Claims ABSTRACT OF THE DISCLOSURE In the preparation of acrylic acid by the gas phase catalytic oxidation of acrolein with molecular oxygen in the presence of steam, a process wherein the oxidation is effected in the presence of a catalyst composition corresponding to the formula: Mo,V (Li SO O wherein a, b and d represent respectively the number of atoms and c is the mol number of lithium sulfate, and wherein a is 12, b is 0.1 to 9.0, c is 0.1 to 9.0 and d is 36.25 to 58.5. The catalyst composition has a high catalytic activity with a long catalytic life, and acrylic acid is produced in an excellent yield with a high purity by the use of such composition.

The present invention relates to a process for the preparation of acrylic acid. More particularly, it relates to a process for the preparation of acrylic acid by the gas phase catalytic oxidation of acrolein in the presence of a specific catalyst composition.

For the gas phase catalytic oxidation of acrolein to produce acrylic acid, there have been known various catalyst compositions: e.g. a catalyst composition comprising molybdenum oxide and vanadium oxide deposited on silica gel [Japanese patent publication No. 1,775/ 1966], a catalyst composition comprising oxides of molybdenum, vanadium and arsenic deposited on silica [Japanese patent publication No. 16,604/1967], a catalyst composition comprising molybdenum oxide and vanadium oxide deposited on aluminum sponge [Japanese patent publication No. 11,647/ 1969], a catalyst composition comprising oxides of molybdenum, vanadium and aluminum with an additional other metal oxide [Japanese patent publication No. 26,287/ 1969], etc. These catalyst compositions have a relatively high catalytic activity. But, the catalytic activity is considerably varied with the preparation method, and it is diflicult to obtain a catalyst composition having a stable and constant catalytic activity. Moreover, their catalytic life is relatively short.

As the result of the extensive study seeking a catalyst composition for the gas phase catalytic oxidation of acrolein to acrylic acid overcoming the drawbacks as seen in conventional catalyst compositions, it has now been found that the incorporation of lithium sulfate into a catalyst system comprising molybdenum oxide and vanadium oxide nium molybdate and of lithium sulfate are added thereto, affords a catalyst composition which has a much longer catalytic life with a higher catalytic activity than any conventional one. Advantageously, the catalytic activity of such catalyst composition is stable and constant without any considerable variation depending on the preparation method. It is also advantageous that such catalyst composition gives a good conversion of acrolein and a favor- "ice able selectivity to acrylic acid so that acrylic acid can be produced at an excellent yield in a high purity.

For instance, the gas phase oxidation of acrolein using such catalyst composition at 300 C. with a space velocity of 1,000 litre'gas/litre-catalyst/hr. gives the following results:

After 4 hours: conversion of acrolein, 99.8%; selectivity to total-acids (this term indicating all kinds of acids produced and by-produced by the catalytic oxidation of acrolein), 94.7%; selectivity of acrylic acid, 92.6%; per pass yield of acrylic acid, 92.4%; acrylic acid content in total-acids, 98.2% by weight.

After 1200 hours: conversion of acrolein, 97.6%; selectivity to acrylic acid, 92.1%; per pass yield of acrylic acid, 89.9%.

According to the present invention, there is provided a process for the preparation of acrylic acid by the gas phase catalytic oxidation of acrolein with molecular oxygen in the presence of steam at an elevated temperature using a catalyst composition corresponding to the formula: Mo,V (Li SO O wherein a, b and d represent respectively the number of atoms and c is the mol number of lithium sulfate, provided that, in case of a being 12, b is 0.1 to 9.0, c is 0.1 to 9.0 and dis 36.25 to 58.5.

For preparation of the catalyst composition, there are employed a molybdenum source (e.g. ammonium molybdate, molybdenum oxide, molybdic acid), a vanadium source (e.g. ammonium metavanadate, vanadium pentoxide) and a lithium sulfate source. As the lithium sulfate source, there may be used lithium sulfate itself or the combination of any lithium salt (e.g. lithium nitrate, lithium carbonate) with sulfuric acid.

The catalyst composition may be composed of the s id essential sources only but favorably further with a suitable carrier (e.g. silica sol, silica gel, alumina, aluminum sponge, silicon carbide, diatomaceous earth, titanium oxide). Silica sol is a particularly preferred carrier. The amount of the carrier is varied with its kind and may be usually less than by weight, preferably from 5 to 90% by Weight, of the catalyst composition.

The preparation of the catalyst composition may be executed by a per se conventional procedure: e.g. ammonium metavanadate is dissolved in an aqueous solution of oxalic acid for reduction, aqueous solutions of ammonium molybdate and of lithium sulfate are added thereto, and the resulting mixture is admixed with a carrier (e.g. silica sol); the resultant slurry is evaporated at to C. to dryness, heated to 250 C. in 2 hours and then calcined at 250 C. for 3 hours; the resultant cake is crushed, admixed with graphite, pelletized and calcined in the atmosphere at 350 C. for 6 hours.

The production of acrylic acid using the catalyst composition of the invention may be effected by a fluidized bed process or a fixed bed process. The particle size of the catalyst composition is not particularly limited and may be optionally varied with the type of its use.

The gaseous mixture to be contacted with the catalyst composition may contain 0.5 to 4 mol (preferably about 0.8 to 2.5 mol) of oxygen and 1 to 20 mol (preferably about 5 to 15 mol) of steam per 1 mol of acrolein. The space velocity of the gaseous mixture is usually from 360 to 4,000 litre-gas/litre-catalyst/hr., preferably from 450 to 1,800 1itre-gas/litre-catalyst/hr.

As the oxygen source, there may be used pure oxygen gas, air enhanced or not in oxygen concentration or any other molecular oxygen-containing gas. From the economical viewpoint, the use of air is preferred. As the case may be, steam is introduced into the reaction system. If desired, an appropriate inert gas such as nitrogen, carbon dioxide or argon may be used as a diluent.

was generated. After the generation of carbon dioxide ceased, there was obtained a dark blue aqueous solution of vanadyl oxalate, which was added to the above prepared aqueous molybdate solution. A solution of lithium.

The reaction temperature for the oxidation of acrolein sulfate (LiSO -H O) (50.5 parts by weight) in water (400 is associated with the kind of the catalyst composition and parts by weight) was incorporated therein. Then, silica may be usually from 250 to 400 C., favorably from 801 containing 20% (by weight) SiO (900 parts by 270 to 350 C. The reaction pressure maybe around atweight) was added thereto. The resultant mixture was mospheric pressure, preferably from 0.7 to 5 absolute evaporated at 100 to 150 C. to dryness. The dried, mat 1Q terial was charged in an electric furnace, and the tem- As illustrated above, the catalyst composition ofrthe perature was elevated to 250 C. in 2 hours. Calcination invention is characteristic in showing a high catalytic was carried out at the same temperature for 3 hours. The activity and a long catalytic life in the oxidation of calcined material was crushed, about 2% by weight of acrolein to acrylic acid. Thus, the process of this invengraphite was admixed therewith and the resultant mixtion can afford acrylic acid in an excellent yield witha 5 turewas pelletized. The pellets were calcined at 350 C. high it for 6 hours, crushed and passed through a sieve to give a Practical and presently preferred embodiments of the catalyst composition corresponding to the formula: present invention are illustratively shown in the follow- Mo V (Li SO O of to 16 mesh. ing examples wherein: The above prepared catalyst composition (25 ml.) was Reacted acrolein (m 01) 2 charged 1n a glass made reactor of mm. 1n inner diameter. A gaseous mixture of 5.0 mol percent of acrolem, =Feed acrolem (mol) Unreacted acrolem (mol) 7.5 mol percent of oxygen, 57.5 mol percent of nitrogen and 30.0 mol percent of' steam was fed into the reactor Converslon of acmlem V at a space velocity of 1,000 litrergas/litrecatalyst/hr.

=R6a0ted {4011316111 X100 and contacted with the catalyst composition at 300 C.

Feed acrolein (mol) The obtained results were as follows: conversion of acrolein, 99.8%; selectivity to total-acids, 94.7%; selecselectlvlty t0 total-301615 tivity to acrylic acid, 92.6%; per pass yield of acrylic Total-acids (in terms of acrylic acid) (mol) X 100 acid, 92.4%; purity of acrylic acid in total-acids, 98.2%

Reacted acrolein (mol) y Weight- 1 1 d EXAMPLES 2 T023 Se ectlvlty to any 16 am l As in Example 1 but varying the proportion of am- WE QQ X 100 monium metavanadate (NH VO ammonium molybdate Reacted acrolem ((NHQ Mo O -4H O) and lithium sulfate Yield of acrylic acid (L1SO -H O) Produced acrylic acid (mol) X 100 there were prepared a number of catalyst compositions. F d l i l) The reactions were carried out using these catalyst compositions under the same reaction conditions as in Exgg gfif gigigi ggi were made by gas chromatography 4Q ample 1 but varying the reaction temperature.

' The results are as shown in Table 1.

TABLE 1 Catalyst composition Selec- Selec- Reaction Convertivity tivit Number of atoms tempersion of to totalto acrylic Yield oi number ature acrolein acids acid. acrylic acid. Example N0. M0 'V Li SO 0.) (percent) (percent) (percent) (percent) 12 0. 5 0. 5 325 97. 7 89. 1 87. 5 85. 1 12 0. 5 1. o 320 98. 4 87. 8 86. 3 84. 9 12 0. 5 4. 0 325 100 90. 3 88. 6 88. 6 12 1.0 1.0 312 98.4 90.7 89.8 88.4 12 1. 0 2. 0 315 98. 7 93. 3 92. 1 90. 9 12 1. 0 4. 0 318 99. 2 92. 7 90. 1 89. 4 12 1. 0 6. 0 310 100 92. 3 90. 7 90. 7 12 2.0 0.5 318 100 91.9 90.2 90.2 12 2. 0 4. 0 316 100 93. 8 91. 7 91. 7 12 2.0 6.0 330 98.8 91.7 90.7 89.6 12 2. 0 9. 0 338 94. 1 91. 8 91. 4 86. o 12 4. 0 1. 0 320 100 91. 8 89. 4 89. 4 12 4.0 2.0 320 98. 3 92. 5 90. 1 89.2 12 4.0 4.0 328 95.5 91.6 91.2 87.1 12 4.0 9.0 332 100 90.2 85.8 85.8 12 6.0 1,0 320 98.0 91.2 90.6 88,8 12 6. 0 2, 0 305 100 90.0 89. 0 89. 0 12 6. 0 4. 0 305 100 88. 4 85.9 85. 9 12 6.0 6.0 328 95.8 91.6 89.5 85.7 12 6.0 9.0 335 97.4 90.5 87.8 85.5 12 9. o 2. 0 334 97.8 90.8 88. 0 86.1 12 9.0 4.0 342 96.2 90.2 87.7 84.4

EXAMPLE 1 Into a solution of 28% (weight by weight) ammonia water (360 parts by weight) in water (500 parts by weight), ammonium molybdate ((NH Mo O -4H O) (425 parts by weight) was dissolved. Separately, oxalic acid (116 parts by weight) was dissolved in water (300 parts by weight) while heating, 'and then ammonium metavanadate (NH VO (47 parts by weight) was dissolved therein under heating. The ammonium metavanadate was reduced with oxalic acid and carbon dioxide REFERENCE EXAMPLES 1 to 12 The results are as shown in Table 2.

3. The process according to claim 2, wherein the carrier is silica sol.

TAB LE 2 Catalyst composition Selec- Reaction Conver- Selectivity to Yield of Number of atoms M01 number temperasion of tivity to acrylic acrylic Reference ture acrolein total-acids acid acid Example N0. M V LiNO; H280 LizSO; C.) (percent) (percent) (percent) (percent) EXAMPLE 24 4. The process accordlng to clalm 1, wherein the Using the catalyst composition as in Example 1, the reaction was carried out continuously under the same reaction conditions as in Example 1.

The results are as shown in Table 3.

What is claimed is:

1. In the preparation of acrylic acid by the gas phase catalytic oxidation of acrolein with molecular oxygen in the presence of stream, a process wherein a gaseous mixture comprising acrolein, oxygen and steam is contacted at an elevated temperature with a catalyst consisting essentially of the composition corresponding to the formula: Mo V (Li SO O wherein a, b and d represent respectively the number of atoms and c is the mol number of lithium sulfate and wherein a is 12, b is 0.1 to 9.0, c is 0.1 to 9.0 and d is 36.25 to 58.5.

2. The process according to claim 1, wherein the catalyst is supported on a carrier.

oxygen source is air.

5. The process according to claim 1, wherein the gaseous mixture comprises 0.5 to 4 mol of oxygen and 1 to 20 mol of steam per 1 mol of acrolein.

6. The process according to claim 5, wherein the gaseous mixture comprises 0.8 to 2.5 mol of oxygen and 5 to 15 mol of steam per 1 mol of acrolein.

7. The process according to claim 1, wherein the contact is effected at a temperature of from 250 to 400 C.

8. The process according to claim 7, wherein the contact is effected at a temperature of from 270 to 350 C.

9. The process according to claim 1, wherein the contact is effected at a space velocity of 360 to 400 litre-gas/ litre catalyst/ hr.

10. The process according to claim 9, wherein the contact is eifected at a space velocity of 450 to 1,800 litregas/litre catalyst/hr.

References Cited FOREIGN PATENTS 411,775 4/1973 Japan 260-530 N LORRAINE A. WEINBERGER, Primary Examiner R. D. KELLY, Assistant Examiner U.S. Cl. X.R. 252-440 

